1. Field of the Invention
The present invention relates to rail car braking systems and, more particularly, to a warning indicator reflecting low brake cylinder pressure and brake system leakage into the brake cylinder.
2. Description of the Related Art
Control valves used in freight car brake systems, such as the DB-60 control valve manufactured by New York Air Brake Corporation of Watertown, N.Y., or the AB-type control valves manufactured by Wabtec Corporation of Wilmerding, Pa., typically supply air pressure to the brake cylinder of a freight car. If the brake cylinder or the plumbing between the control valve and the car has a leak, however, the brake cylinder will not maintain the original set pressure. In addition to brake cylinder leakage, resulting in low brake cylinder pressure, the brake system can leak into the brake cylinder, resulting in high brake cylinder pressure.
Recent improvements to AAR brake systems include the addition of brake cylinder maintaining valves, which compensate for brake cylinder leakage. Another improvement includes the addition of a brake cylinder limiting valve, which exhausts brake cylinder over-pressure resulting from leakage into the brake cylinder. While these improvements may improve the overall safety of the brake system, they may obscure the presence of brake defect, making detection more difficult and thereby delaying corrective action. As a result, there is a need for a system that can provide a clear indication when the braking system low brake cylinder pressure or brake system leakage into the brake cylinder.